eca-engine: do not stop transport with engine-halt
eca-engine: do not stop transport with engine-halt

This patch allows to remove ecasound from JACK with engine-halt without
stopping JACK transport for other clients. Ecasound can later reattach
to the JACK graph with engine-launch and resume from the same position.

jeremysalwen/Ecasound-LV2,jeremysalwen/Ecasound-LV2,jeremysalwen/Ecasound-LV2,jeremysalwen/Ecasound-LV2,jeremysalwen/Ecasound-LV2